The invention relates to a damper valve for couplings for hydraulic lines, in particular those connecting a hydraulically actuated servomotor displacement assembly of a servo control to a servo valve. The damper valve according to the invention has an aperture-disc-like valve carrier whose apertures through which hydraulic medium flows can be controlled by means of small valve spring plates fastened to the end face of the carrier part by bolts, and/or spring-mounted valve plates.
In order to minimize the forces which must be applied by the driver of a motor vehicle when actuating the vehicle steering system, today's vehicles (at least passenger cars) are typically equipped with a hydraulically actuated power steering system. In this context, German patent document DE-A 40 29 156 discloses an arrangement in which a dual-action piston-cylinder assembly (which serves to generate an auxiliary hydraulic force) also acts as a steering damper. For this purpose, damper elements are arranged in the lines between the piston/cylinder assembly and the servo valve, so as to connect the piston/cylinder assembly to a hydraulic pressure source or a relatively pressureless hydraulic reservoir, in a controllable manner. However, this structure is comparatively complicated. The same applies to a similar arrangement described in German patent document DE-A 41 06 310.
According to an unpublished German patent application P 43 23 179.9, it was proposed to arrange the damper valves on an aperture-disc-like carrier whose apertures (through which hydraulic medium flows) can be controlled by means of small valve plates fastened by bolts to the end face of the valve carrier, and/or spring-mounted valve plates. In this case, provision is made for the aperture-disc-like valve carrier to be tensioned in the manner of a spacer ring or a spacer disc between a bearing surface of a connector arranged on the housing of the servo valve or the piston/cylinder assembly and a counter-bearing surface of the connection part of the line which can be connected to the connector. The assembly can be substantially simplified by these measures.
German patent document DE 78 12 642 U1 discloses a nonreturn valve for aerating and venting fuel tanks, which has a two-part housing arranged between two line parts. One housing half must be connected to the one line part, and the other must be connected to the other line part. (The connecting means is not illustrated in detail.) When the housing parts are fitted together, an annular membrane is inserted between them so that its outer circumference is held firmly in the housing in an inner circumferential groove remaining between the housing halves. This annular membrane interacts with an insert which serves as a valve seat body, and is anchored firmly and captively in one housing half.
In this known arrangement, faulty assembly is very possible due either to a failure to insert the annular membrane between the housing halves when they are joined together on the one hand, or assembly of the housing between the lines in an incorrect direction on the other.
The object of the present invention is to provide an improved damper valve of the type specified above.
This object is achieved according to the invention, by arranging the valve carrier firmly or captively on the line-side connection part and arranging the small valve spring plates and/or valve plates captively on the valve carrier. The invention is based on the general concept of integrating the damper valves in the line-side connection parts of the hydraulic lines so that the valves are connected captively to the connection parts and are thus necessarily arranged correctly during the assembly of the hydraulic system.
According to a preferred embodiment of the invention, the connection part is designed essentially in the shape of a cylindrical cup, with an opening at one end. Radial openings, spaced axially from the open end, are arranged axially between an external thread on the connection part and a radial flange at the other end, and communicate via openings in the aperture-disc-like valve carrier with the above-mentioned end-face opening. Connection parts of this type can be combined with hydraulic lines which have rings at their ends, which rings can be fitted axially onto the connection parts and have an annular groove that is open towards the inner circumference of the ring, communicates with the hydraulic line, and is capable of communicating via said annular groove with the radial openings in the connection part. During the assembly of the hydraulic system, the connection parts then serve as holding screws for the above-mentioned rings, sealing rings being arranged on both sides of the ring in order to seal off, on the one hand, the joint between the ring and the flange of the connection part and, on the other hand, the joint between the ring and the housing, connected to the hydraulic line, of the respective hydraulic system part, for example, servo valve or servomotor.
In a preferred embodiment, the connection part can be fitted together, for example by welding, from two parts, one part forming the axially closed end of the connection part and the other part being formed integrally with the aperture-disc-shaped valve carrier.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.